For certain packaging material grades, especially such materials which are intended to be used for food stuffs, beverages, etc., a sterilization of the surface thereof is required in order to minimize the contribution of microorganisms from the packaging material to the product duct to be contained therein. One of said sterilization methods involves the use of hydrogen peroxide as the sterilization agent, There are different methods of applying said hydrogen peroxide to the packaging material, such as by passing the packaging material through the hydrogen peroxide, immersing said material in said hydrogen peroxide, applying a film of hydrogen peroxide to the surface of the packaging material, etc., but generally the hydrogen peroxide is utilized in the form of a solution thereof, especially an aqueous solution.
Although the packaging material has generally been made hydrofobic during the manufacture thereof, in order to make it resistant to the penetration of aqueous liquids including a hydrogen peroxide solution, the hydrogen peroxide is usually utilized in such a concentration and at such a temperature that a penetration thereof into the packaging material is not easily avoided. The hot aquecus hydrogen peroxide solution especially penetrates the edges of the packaging material, but also in a case where for some reason the packaging machine has to be stopped, there will be a great risk of having a penetration of the hot hydrogen peroxide into the packaging material to loosen up the same. When restarting the machine part of the packaging material has to be discarded or else there will be a risk of having a bursting of any package inside the machine which means a cleaning operation for several hours.
Thus, in summary, there is no available system today which will impart to the packaging material such a degree of hydrofobicity that a penetration of a concentrated and hot hydrogen peroxide solution is avoided.